Needle plates provided in conventional sewing machines are screw fastened to the upper surface of the sewing machine bed. Such needle plates are typically provided with a needle hole allowing penetration of a sewing needle and angular holes through which a feed dog for feeding a workpiece cloth is driven up and down. Within the bed below the needle plate, a horizontal hook mechanism is provided. When the horizontal hook mechanism needs to be accessed, for instance, to remove thread caught up in the horizontal hook mechanism or to clean the horizontal hook mechanism and its surroundings for maintenance purposes, the needle plate is removed by loosening the screw to expose the horizontal hook mechanism and its surroundings. When reattaching the needle plate to the bed, the needle plate needs to be carefully located with the sewing needle and the feed dog. Mislocation of the needle plate may cause unwanted contact with the sewing needle and the feed dog, possibly leading to mechanical damages.
To address such concerns, a needle plate was conceived that comprises a first needle plate provided with a needle hole and angular holes, and a second needle plate situated above the horizontal hook mechanism. This type of needle plate is provided with an engagement mechanism for establishing engagement between the first needle plate and the second needle plate, and a disengagement button that cancels the engagement of the engagement mechanism through user operation performed from the top side of the needle plate. The engagement mechanism is provided with a protrusion that is formed at the first needle plate and a slot being defined on a leaf spring provided at the second needle plate, which are mated to establish the engagement. The engagement is cancelled by depressing the disengagement button. Thus, second needle plate alone can be removed from the bed with the first needle plate staying secured on the bed.
The above described configuration, however, requires a two-step operation to remove the second needle plate. More specifically, the two-step operation includes a first operation in which the disengagement button is depressed against the elasticity of the leaf spring and a second operation in which the second needle plate is pulled away from the first needle plate while the disengagement button is depressed. However, not only is the two-step operation cumbersome but is also hard to carry out because the first operation is performed in one direction and the second operation is performed in another.